Watercraft

ABSTRACT

There is described a watercraft ( 1 ), comprising a hull ( 6 ) pivotally mounted for rotation about a longitudinal axis ( 10 ) relative to a float assembly ( 2, 3 ) having only two stable floating positions. The float assembly may comprise two spaced floats extending longitudinally of the watercraft and joined by transverse spars ( 4, 5 ), the hull being mounted between the transverse spars. Alternatively, the watercraft may comprise a first float assembly ( 27 ) mounted to a forward end of the hull and a second float assembly ( 33 ) mounted to an aft end of the hull, each float assembly comprising a pair of floats ( 28, 29; 35, 36 ) spaced transversely from the longitudinal axis of rotation of the hull.

The present application relates to watercraft, and is particularly concerned with providing a craft in which the effects of rolling motion on passengers, crew and cargo can be reduced.

The present invention provides an aquatic vessel having a hull pivotally supported at its fore and aft ends on one or two float assemblies. The main hull is supported by the float assembly or assemblies for rotation about a longitudinal axis. The float assemblies are arranged to have two stable floating positions, angularly spaced by 180 degrees about a longitudinal axis of the vessel.

In one aspect, the present invention provides a watercraft comprising a hull pivotally mounted for rotation about a longitudinal axis relative to a float assembly comprising a pair of spaced floats.

In one embodiment, the float assembly comprises a pair of spaced floats extending longitudinally of the watercraft and joined by two transverse spars, the hull being mounted between the transverse spars. The floats are positioned angularly symmetrically about the longitudinal axis of rotation.

In a second aspect, the watercraft comprises a first float assembly mounted to a forward end of the hull and a second float assembly mounted to an aft end of the hull. In one embodiment the first and second float assemblies may each comprise a single float having orthogonal axes of symmetry intersecting on the longitudinal axis of rotation of the hull.

In another embodiment, the first and second float assemblies may each comprise two floats equally spaced transversely from the longitudinal axis of rotation of the hull. It is foreseen that the first and/or the second float assembly may alternatively comprise three or four floats arranged in a transverse row.

The hull may comprise propulsion means extending from the hull and adapted to be immersed when the craft is afloat, for a example a propeller. The hull may be supported clear of the water by the float assemblies, or may be held with part of the hull immersed.

The watercraft may further include means to selectively prevent relative rotation between the hull and the float assembly or assemblies. The float assembly or assemblies may be selectively lockable in one or more angular positions relative to the hull.

In one embodiment, the hull is provided with a sensor such as a gyroscope to determine the orientation of the hull relative to the vertical, and control means to operate an actuator to rotate the hull relative to one or more of the float assemblies so as to maintain the hull in its vertical orientation.

Embodiments of the invention will now be described in detail with reference to the accompanying drawings, in which:

FIG. 1 is a plan in view of a catamaran-type craft according to the invention;

FIG. 2 is a side in view of the craft of FIG. 1, seen in section along the line of A-A FIG. 1;

FIG. 3 is a schematic perspective view of an alternative craft constructed according to the invention;

FIG. 4 is a schematic view of the craft of FIG. 3 from the rear;

FIG. 5 is a perspective view of a further alternative craft embodying the principle of the invention; and

FIG. 6 shows an arrangement for selectively locking and unlocking the rolling motion of the hull of the craft.

In watercraft of the present invention, the hull in which the passengers or load are carried is pivotally supported by floats, so that the hull can rotate relative to the floats about a longitudinal axis of the vessel. In this way, even in rough water the hull can remain stable and upright while the floats follow the surface of the water.

Referring now to FIGS. 1 and 2, there is seen a catamaran-type vessel 1 including a float assembly comprising left and right floats 2 and 3 joined together by transversely-extending forward and rear spars 4 and 5. Mounted between the forward and rear spars 4 and 5 is a central hull 6 with a cockpit structure 7. The hull is mounted to the spars 4 and 5 by forward 8 and rear 9 pivoting joints, which will be described in detail later. The clearance between the hull 6 and the floats 2 and 3 is such that the hull 6 may rotate through 360° about a rolling axis, relative to the float assembly.

The form of the floats 2 and 3 of the float assembly is such that they are each symmetrical about a horizontal plane H-H seen in FIG. 2, as well as being symmetrical about a vertical plane V-V seen in FIG. 1. The float assembly thus has two stable floating positions, angularly spaced by 180 degrees relative to the longitudinal axis of the hull. In this way, the floats 2 and 3 perform equally well which ever way up the assembly of floats 2 and 3 and spars 4 and 5 is supported on water. The buoyancy of the floats 2 and 3 may be arranged so that the hull 6 is supported clear of the water's surface WL as seen in FIG. 2. Alternatively, the hull may be supported so that its underside is in the water. In either case, the hull may be provided with a self-draining cockpit in which the cockpit floor is held above the vessel's waterline, and drains are provided in the hull to allow the egress of water from the cockpit.

The vessel 1 may be propelled by a conventional propeller (not shown) mounted below the hull 6 and driven by a motor mounted within the hull.

The pivoting joints 8 and 9 permit rolling movement of the hull 6 relative to the floats 2 and 3, about a horizontal pivoting axis 10 aligned with the fore-and-after direction of the vessel. The centre of gravity G of the hull 6 is arranged to be spaced below the pivoting axis 10 when the hull is level, such that the hull 6 tends to remain level irrespective of any rolling inclination of the catamaran floats 2 and 3.

The pivoting joints 8 and 9 may include locking means to selectively prevent relative rotation between the hull 6 and the floats. When the vessel is in harbour, or operating in calm water, the pivoting joints may be locked to prevent unwanted rolling of the hull, for example as passengers move around inside the hull and the position of the centre of gravity G of the hull consequently moves in the transverse direction.

The pivoting joints 8 and 9 may also, or alternatively, include damping means to damp out rolling oscillations in the hull, so that any rolling movement of the hull is suppressed within a few oscillations. The damping means could be friction elements within the joints 8 and 9, or damping elements may be connected between the hull 6 and the spars 4 and 5. The joints may include adjustment means to vary the degree of damping applied to the rolling motion.

When the vessel is operating in rough water, the floats 2 and 3 will follow the surface of the water, exhibiting pitching, rolling and heaving motion. While the pitching and heaving motion is transmitted through the floats to the hull 6, the rolling motion of the floats is not transmitted to the hull due to the pivoting action of the joints 8 and 9. This results in a more comfortable ride for the passengers within the hull, as the hull remains generally stable in roll. Furthermore, in the event of a capsize of the vessel due to the influence of large waves, for example, the floats 2 and 3 will quickly regain their stable positions on the water surface, but after a capsize the left float 2 will be on the right of the hull 6, and the right float 3 will be on the left. The hull 6 will rotate through 180° relative to the floats, either during or after the capsize, to regain its upright position. The vessel can continue to navigate, since the floats are symmetrical and operate equally well in both positions of the catamaran floats. This is clearly advantageous over conventional catamaran craft which, when capsized, are very difficult to right due to their inherent initial stability in roll when inverted.

FIGS. 3 and 4 show perspective and end views of an alternative arrangement of the watercraft of the present invention. In this arrangement, a hull 16 is mounted at its fore and aft ends to a pair of floats 17 and 18. The floats are configured to have symmetry about two orthogonal axes, so that the floats may be stably supported on a horizontal water surface in two positions angularly spaced by 180 degrees. The floats 17 and 18 are pivotally mounted at the respective ends of the hull 16 by pivoting joints 22, in the same way that the spars 4 and 5 of the previous embodiment are mounted to the hull 6. The floats 17 and 18 may be independently rotatable relative to the hull, or may be fixed to a common shaft to rotate together. One or more propellers 23 and optionally a rudder (not shown) extend downwardly from the hull 16, positioned so as to be immersed in water when the vessel is floating. As before, locking and/or damping arrangements may be provided at the pivoting joints 22, to provide selective control over the relative movement of the hull 16 and the floats 17 and 18.

In operation, the buoyancy of the floats 17 and 18 is arranged such that the floats will support the hull 16 clear of the water surface WL as seen in FIG. 4. When the vessel is operating in calm water or in harbour, one or both of the pivoting joints 22 may be locked to prevent unwanted rolling motion of the hull 16. When the vessel is operating in rough water, the pivoting joints 22 are freed so that rolling movements of the floats 17 and 18 are not transmitted to the hull 16, which remains substantially stable. As before, the centre of gravity of the hull 16 is positioned below the pivot axis extending between the joints 22, to maintain the hull 16 in its desired position.

In extremely rough conditions, a wave may strike the vessel and lift one or both of the floats, causing the floats to rotate through 180° relative to the hull 16 and reach a stable position inverted relative to its former position. During this rotation, the hull 16 pivots about the joints 22 to remain in its stable upright position, and at the vessel can continue to navigate, driven by the propeller 23 and steered by the rudder.

A further alternative vessel according to the present invention is illustrated schematically in FIG. 5. In the vessel of FIG. 5, a central hull 26 has mounted to its forward end a first float assembly 27, comprising a pair of floats 28 and 29 connected by a transverse spar 30. The spar 30 is mounted to the hull 26 by a pivoting joint 31, which permits the floats 28 and 29 and the spar 30 to rotate relative to the hull 26 about a longitudinal axis 32.

Mounted to the rear of the hull 26 is a second float assembly 33, comprising a pair of floats 34 and 35, connected by a spar 36 mounted to the hull 26 by a pivoting joint 37. The pivoting joint 37 permits the floats 34 and 35 and the spar 36 to rotate relative to the hull 26 about the longitudinal axis 32.

As in the embodiment illustrated in FIGS. 1 and 2, the floats 28, 29, 34 and 35 are preferably performed so as to be symmetrical about vertical and horizontal axis, so that both float assemblies have two stable floating positions. One or both of the float assemblies 27 and 33 may be inverted relative to the hull, and the float assemblies are still able to support the hull 26 for navigation. As before, the buoyancy of the floats may be arranged such that the hull 26 is supported clear of the water surface.

The centre of gravity of the hull 26 is arranged to be below the longitudinal axis 32, to maintain the hull in the desired upright position. Since in this embodiment the floats 28 and 34 and the floats 29 and 35 on either side of the hull 26 are spaced in front of and behind the hull, it is possible to erect superstructures such as a mast and sailing rig 38 (shown in phantom line in FIG. 5) to extend upwardly from the hull, without the risk of such superstructures contacting the float assemblies as they rotate relative to the hull. Likewise, a keel assembly 39 (shown in phantom line in FIG. 5) may be provided on the hull 26 to increase the stability of the hull in roll.

As before, the pivoting joints 31 and 37 may be provided with locking means to selectively prevent relative rolling motion between the float assemblies 27 and 33 and the hull 26. FIG. 6 illustrates an example of such a lockable pivoting joint.

Referring out to FIG. 6, there is shown to an enlarged scale a part of the spar 30 which connects the floats 28 and 29 of the float assembly 27. A shaft 40 is pivotally received in the spar 30, and the hull 26 is mounted on the shaft 40. Fixed to the spar is a disc 41 through which a first opening 42 penetrates. Attached to the shaft 40 and rotatable therewith relative to the spar 30 is a moving disc 43 through which extends a second opening 44. The first and second openings and 42 and 44 are positioned such that they are in alignment when the spar 30 is horizontal and the hull 26 is in its upright position.

A bolt mounting 45 is provided on the spar 30, through which a bolt pin 46 is axially movable. In the position shown in FIG. 6, the bolt pin 46 is in a retracted position, and the moving disc 44 is free to rotate relative to the fixed disc 41. In this position, the float assembly 27 may move in rotation relative to the hull 26.

When the vessel is navigating in calm water, or is in harbour, the spar 30 will adopt a horizontal position and the hull 26 its upright position, bringing the first opening 42 and at the second opening 44 into alignment with the bolt pin 46. By advancing the bolt pin 46 through the opening 42 and into the opening 44, relative rotation between the fixed disc 41 and the moving disc 43 is prevented. This in turn prevents rolling motion of the float assembly 27 relative to the hull 26. Further openings such as 47 and 48 may be provided in the moving disc 43, to provide a number of alternative positions in which the hull 26 may be locked relative to the float assembly 27. These alternative positions may be used, for example while navigating under sail, to set a degree of heel for the hull 26.

As an alternative to the bolt pin 46, the discs 41 and may be provided, on their facing surfaces, with friction material and a clamping device (not shown) may be provided to exert a clamping force bringing the two disks together, so that the friction material resists relative movement of the disks in rotation. By controlling the clamping force, the freedom of the float assemblies 27 and 33 to rotate relative to the hull 26 may be controlled.

Embodiments of the invention have been illustrated in the accompanying Figures with float assemblies having two floats. It is, however, foreseen that a vessel similar to that of FIG. 4 may be provided, wherein each spar 36 has four or more floats provided along the length of the spar rather than the two shown in the Figure. In a particular embodiment, four floats are arranged side-by side along a spar.

In relation to the embodiments illustrated in FIGS. 1 to 4, the proportion of the craft has been described as being by means of a propeller and rudder which extend from the central hull 6 into the water. Alternatively, a motor mounted in the hull 6 may drive a shaft extending along the pivot axis 10 (seen in FIGS. 1 and 2) and through the joint 9. This shaft may drive a transmission system linked to two propellers, one positioned below the spar 5 and one positioned above it. The positions of the propellers will be arranged such that one of the propellers is in the water, when the floats 2 and 3 are supported on the water surface. The transmission system preferably directs the power from the motor only to the propeller which is immersed, but if a simpler system is required then both propellers could be driven simultaneously when the craft navigates under power. In this arrangement, most of the power will be transmitted to the immersed propeller as it will offer more resistance than the propeller running in air.

In the same manner, steering of the craft may be arranged by means of a pair of rudders extending upwardly and downwardly from the spar 5, and controlled from within the hull 6.

In a further alternative arrangement, the vessel may be propelled by a water jet. In one embodiment, water may be drawn up from beneath the hull and expelled through a jet coaxial with the pivot axis 10 at the rear of the hull. The vessel may be steered by directing the jet to one side or the other.

While the invention has been described in relation to the provision of a stable hull platform for vessels in rough weather, it is equally foreseen that smaller versions of the vessel according to the invention may be provided, for example for use in water park rides. Such vessels may have reduced stability built into them, by arranging the centre of gravity of the hull to be closer to the pivot axis of the float assembly or assemblies.

In a further embodiment (not illustrated) the hull is provided with sensor means to detect the orientation of the hull relative to the vertical, actuator means to rotate the hull about the longitudinal axis relative to the float assembly or assemblies, and control or means responsive to an output of the sensor to control the actuator so that the hull is maintained in a vertical orientation as the floats rotate relative to the longitudinal axis to follow the surface of the water. In this embodiment, the centre of gravity of the hull may be positioned on, or even above, the rotation axis of the hull relative to the float assemblies, since the hull will be maintained vertical by the actuator rather than by gravity. The actuator may be an electric motor, or may be a hydraulic actuator, mounted in the hull and driving the shaft which connects the hull to one or both of the float assemblies. The sensor means may be a gyroscopic sensor, or simply a damped pendulum pivoting about an axis parallel to the longitudinal axis of the hull. The control means may include a microprocessor, and may be programmable to maintain the hull either vertical or at a predetermined angle of heel, as the float assemblies rotate relative to each other and to the hull. 

1. A watercraft, comprising a hull pivotally mounted for rotation about a longitudinal axis relative to a float assembly, wherein the float assembly has only two stable floating positions angularly separated by 180 degrees about a longitudinal axis of the watercraft.
 2. A watercraft according to claim 1, wherein the watercraft comprises a first float assembly mounted to a forward end of the hull and a second float assembly mounted to an aft end of the hull.
 3. A watercraft according to claim 2, wherein the first and second float assemblies each comprise spaced floats extending longitudinally of the watercraft and symmetrically spaced transversely from the longitudinal axis, the floats being joined by a transverse spar, the hull being mounted between the transverse spars of the first and second float assemblies.
 4. A watercraft according to claim 2, wherein the first and second float assemblies each comprise two floats.
 5. A watercraft according to claim 2, wherein the first and second float assemblies each comprise four floats arranged side-by side along a spar.
 6. A watercraft according to claim 2, wherein the first and second float assemblies each comprise a single float having orthogonal axes of symmetry intersecting on the longitudinal axis of rotation of the watercraft.
 7. A watercraft according to claim 1, wherein the float assembly comprises a pair of spaced floats extending longitudinally of the watercraft and joined by two transverse spars, the hull being mounted to the transverse spars for rotation about the longitudinal axis.
 8. A watercraft according to claim 1, wherein the hull comprises propulsion means extending from the hull and adapted to be immersed when the craft is afloat.
 9. A watercraft according to claim 8, wherein the propulsion means comprises a propeller.
 10. A watercraft according to claim 8, wherein the propulsion means comprises a water jet.
 11. A watercraft according to claim 2, further including means to selectively resist or prevent relative rotation between the hull and the float assemblies.
 12. A watercraft according to claim 2, wherein the hull and the float assemblies may be selectively locked in one or more relative angular positions.
 13. A watercraft according claim 2, further including sensor means to detect the orientation of the hull relative to the vertical, actuator means to rotate the hull relative to one or more of the float assemblies, and control means responsive to an output of the sensor means and operable to drive the actuator means to maintain the hull in a desired orientation relative to the vertical.
 14. (canceled) 